a) 17/12 - 9/8 - 17/6 = 34/24 - 27/24 - 68/24 = - 61/24 = -2 13/24
b) 27/4 - 8/3 - 19/6 = 243/36 - 96/36 - 114/36 = 33/36
c) 20/9 - 23/6 + 16/3 = 40/18 - 69/18 + 96/18 = 67/18 = 3 13/18
d) 20/9 + 17/12 - 7/8 = 160/72 + 102/72 - 63/72 = 199/72 = 2 55/72
